A fixed-type constant velocity universal joint (Rzeppa type constant velocity universal joint: BJ) has been employed as a connection joint for a drive shaft or the like of an automobile. For example, such a universal joint includes: an outer race serving as an outer member and having curved track grooves formed axially in a spherical inner diameter surface; an inner race serving as an inner member and having curved track grooves formed axially in a spherical outer diameter surface; a plurality of torque transmission balls arranged in respective ball tracks each constituted by one of the track grooves of the outer race in combination with the corresponding track groove of the inner race; and a retainer having pockets for holding those balls. The plurality of balls are accommodated in respective pockets formed in the retainer and are arranged at regular intervals in the circumferential direction.
When this constant velocity universal joint is employed in a drive shaft, a shaft portion (driven shaft) integrally extending from one end of the outer race in the axial direction thereof is connected to a wheel-bearing apparatus, and a shaft (driving shaft) spline-fitted into a shaft hole of the inner race is connected to a sliding-type constant velocity universal joint. Even when the outer race and the inner race are angularly displaced between the respective two axes of the shaft portion of the outer race and the shaft of the inner race side, each of the balls accommodated in the pockets of the retainer is always held in a plane bisecting an operational angle at any operational angle. Therefore, the constant velocity of the joint is ensured. In this case, the operational angle represents an angle formed by the shaft portion of the outer race and the shaft of the inner race.
As described above, a shaft is connected to the shaft hole of the inner race of a constant velocity universal joint. In this connection structure of the inner race and the shaft, the shaft is spline-fitted to the shaft hole of the inner race, and is prevented from coming off by virtue of a circlip (see, for example, Patent Document 1). In the connection structure disclosed in Patent Document 1, a chamfer is provided at the shaft insertion side end portion of the shaft hole of the inner race so as to facilitate the automatic installation of the circlip.
FIGS. 9 to 12 illustrate how a shaft 113 is installed in an inner race 106 of a configuration as disclosed in Patent Document 1. As shown in the drawings, a spline 117 is formed on the inner peripheral surface of a shaft hole 112 of the inner race 106, and a chamfer 120 is provided at the shaft insertion side end portion of the shaft hole 112. A chamfer angle β is set to be 32.5° or less, more preferably, not less than 15° but not more than 32.5°. Further, in order that the shaft 113 may be allowed to be inserted as it is into the shaft hole 112 of the inner race 106 even in a state in which a circlip 115 previously mounted to a recessed groove 114 formed at an end portion of the shaft 113 is drooping due to the weight of the circlip 115, the radius R2 of the opening end of the chamfer 120 is set larger than the radius R1 when the circlip 115 of the shaft 113 is drooping therefrom due to the weight of the circlip 115 (see FIG. 9).
When installing the shaft 113 in the shaft hole 112 of the inner race 106, as shown in FIG. 9, the shaft 113 is first arranged coaxially with respect to the shaft hole 112 of the inner race 106. Then, a state is attained in which the circlip 115 is drooping from a shaft end portion of the shaft 113.
When, in this state, the shaft 113 is inserted into the shaft hole 112 of the inner race 106 as shown in FIG. 10, the circlip 115 is guided by a tapered surface of the chamfer 120 of the inner race 106 to undergo automatic alignment.
When, thereafter, the shaft 113 is further inserted into the shaft hole 112 of the inner race 106 as shown in FIG. 11, the circlip 115 passes through the shaft hole 112 while reduced to the spline small diameter of the inner race 106.
When, as shown in FIG. 12, the shaft end portion of the shaft 113 is inserted to a position where the shaft end portion of the shaft 113 protrudes from the inner race 106, the circlip 115 is diverged at the position of a step portion 116 formed at the shaft hole opening end of the inner race 106, and the shaft 113 is prevented from coming off by virtue of the circlip 115.    [Patent Document 1] JP 3188001 B